As this sort of medical tool, for example, there is an intravascular free piece capturing tool developed by the present inventor (see Patent Literature 1). The free piece capturing tool is one in which a bag-like filter member having an opening is attached to the tip part of a wire, and by placing the filter member on the downstream side of a surgical operation site in a blood vessel (e.g., a stenosis site in a blood vessel to be dilated by a balloon stent), can capture a thrombus detached by a surgical operation to prevent secondary occlusion of the blood vessel by the detached thrombus.
The filter member described in Patent Literature 1 is formed of a bag-like filter having an opening and an elastic ring for shaping the opening, and the elastic ring is supported by multiple supporting wire members radially extending from the wire. At the beginning, the filter member is contained in a containing member integrally attached to the fore end of a conveying tube with the elastic ring and the filter being folded and elongated. At this time, the wire is also inserted into the conveying tube.
To place such a filter member in a target site, i.e., on the slightly downstream side of the stenosis site, by inserting the containing member containing the filter member into a main catheter preliminarily inserted into the blood vessel, and sending out the conveying tube and the wire together, the filter member is conveyed to the target site.
Then, by without moving the wire, drawing only the conveying tube toward the operating end to move only the containing member backward, the filter member is released out of the containing member. In doing so, the filter member naturally opens the opening by restoring force of the elastic ring, and thereby the filter member is arranged in the blood vessel in an attitude capable of capturing the free piece.
After arranging the filter member in this manner, only the conveying tube is pulled closer, and withdrawn together with the containing member.
Subsequently, along the wire connected to the filter member, a balloon catheter or a stent is sent to the stenosis site to treat the stenosis site.
On the other hand, after withdrawing the balloon catheter after the treatment, it is necessary to withdraw the filter member.
For this purpose, a withdrawing tube different from the conveying tube is sent out from the operating end along the wire. In doing so, the withdrawing tube pushes a small-diameter tube called slider, which is preliminarily arranged on the slightly near to the operating end side of the filter member, and slides the small-diameter tube toward the supporting wire members. This makes the supporting wire members be gradually drawn into the slider, and thereby contractile force toward the center of the elastic ring acts on the elastic ring. The contractile force folds the elastic ring upward and downward in four at positions preliminarily given a tendency, and thereby the elastic ring is formed in an elongated shape to close the opening of the filter.
As described, the withdrawing tube also acts as an actuator to provide external force for closing the opening of the filter member. Subsequently, in that state, the guide wire and the withdrawing tube is pulled closer to withdraw the filter member through the catheter.